High temperature susceptibility measurements: A potential tool for the identification of oil-water transition zone in petroleum reservoirs
High temperature susceptibility measurements: A potential tool for the identification of oil-water transition zone in petroleum reservoirs
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DOI：
10.3389/feart.2022.973385
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发表时间：
2022-09
期刊：
影响因子：
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通讯作者：
M. Abdulkarim;A. Muxworthy;A. Fraser
中科院分区：
文献类型：
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作者：
M. Abdulkarim;A. Muxworthy;A. Fraser
确定油气藏油水过渡带的位置和厚度对储量估算和生产规划具有重要意义。本文描述了一种识别该带的磁学方法。对英国北海中部古近系储层岩心样品的高温磁化率(HT-χ)测量显示，油水界面周围有明显的特征。与主要油段不同，油水界面附近的样品在<；250°C温度下磁化率迅速增加，而在主油段，磁化率增加的速度明显较慢，温度较高。HT-χ数据和穆斯堡尔测量结果表明，蚀变特征的变化是由于油水界面附近六方磁黄铁矿和/或锂镁铁矿的浓度增加所致。在温度为-80°C的储集层中发现了六方磁黄铁矿，而在较深的储集层接触面周围则以纤锌矿为主。这些观察结果表明，六方磁黄铁矿的沉淀与以OWTZ为中心的生物成因活动，即生物降解有关。深部成岩环境中锂辉石的优势与油-水界面的碳氢化合物的水解性以及生物活动的停止有关。
Determining the position and thickness of the oil-water transition zone (OWTZ) in hydrocarbon reservoirs is important to reserve estimation and production planning. This paper describes a magnetic method of identifying this zone. High temperature susceptibility (HT-χ) measurements on core samples from Paleogene reservoirs of the UK Central North Sea revealed distinct signatures around the oil water interface. Rapid increases in susceptibilities at temperatures <250°C were observed for samples around the oil water interface unlike the main oil leg where alteration involving increase in susceptibility occurred at significantly slower rates and higher temperatures. The HT-χ data together with Mössbauer measurements revealed that the variation in alteration characteristics is due to the increasing concentration of hexagonal pyrrhotite and/or lepidocrocite around the oil water interface. Hexagonal pyrrhotite was identified in reservoirs existing at temperatures of <80°C, while lepidocrocite dominated the signature around the contact of deeper reservoirs. These observations suggest that the precipitation of hexagonal pyrrhotite is related to OWTZ centred biogenic activities i.e., biodegradation. The dominance of lepidocrocite in deeper diagenetic settings has been related to hydrolysis of hydrocarbon at the oil water interface, together with cessation of biogenic activities.